According to the Wikipedia article on the species Homo floresiensis, the remains discovered in 2003 consist of unfossilized bones. I would assume that means they are still composed of the original organic material left behind when the human specimen died thousands of years ago. Shoudn't that mean radiocarbon dating would be a good method to date the reamains?

Many articles on Homo floresiensis also discuss how the remains were originally dated to ~12,000 years ago, but that this estimate was later revised to 60–100,000 years ago. However, everything I can find indicates that mostly geological dating methods were used, not radiometric dating.

Why not? The Wikipedia entry on carbon dating says that it can only be used reliably to date specimens up to ~50,000 years, but could carbon dating then at least place a lower limit on the age of these remains? And why wouldn't it have been used back when they thought the specimens were only ~12,000 years old?


2 Answers 2


ScienceMag says:

Rather than damaging the fossils by dating them directly, the team looked to the sediments in which they were found. They discovered pieces of charcoal in sediments at similar depths, and considered those to be proxies for the ages of the fossils themselves. The charcoal bits were dated to around 19,000 and 13,000 to 11,000 years before present.
But Liang Bau boasts a devilishly complicated geological history, as layers of silt and clay interleave with layers of weathered limestone, loose gravel, and volcanic ash. In many places, these layers have been scoured by erosion, altered by seeping water, and jumbled by tectonic activity.
Dating on the gravelly sediment layer containing the fossils suggested it was deposited between 100,000 and 60,000 years ago; just above it is a layer of volcanic ash that was dated to about 60,000 years ago. This suggests that the fossils themselves couldn’t possibly be younger than 60,000 years old, the team reports online today in Nature.
To cap it off, the team has now directly dated the fossils themselves. Originally, researchers shied away from that analysis for fear of damaging them, Tocheri says. But this time, they felt they needed to do it. “It wasn’t until [we] were reasonably convinced that [the fossils] were probably older than 50,000 years old that we decided we needed to date them directly to be absolutely certain,” he says.
The team dated three arm bones found at different locations within the cave during previous excavations. Using uranium-thorium dating—which is based on the radioactive decay of uranium and thorium isotopes in a material—they found dates ranging from about 66,000 to 87,000 years old.

I could not find how the "charcoal bits" were dated, but it would be in the range for carbon dating.


If the fossils, or some of them, were as you describe them with no mineral replacement of the original material, then it would seem that C14 dating would be relevant for the youngest bones at least. If they had original material with adequate carbon in it,C14 is such an obvious method that they must have tried it, or had some very good reason not to. C14 is, like most methods, a tricky technique which doesn't always give accurate results. Perhaps the C14 date didn't tally with other methods they used, so they preferred not to mention it. 50,000 years is pushing the limits pf the C14 method and involves a small amount of the material being destroyed.


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